1. Technical Field
The present invention relates to a liquid ejecting apparatus that is equipped with a plurality of liquid ejecting heads for ejecting liquid retained in pressure chambers through nozzles by applying a pressure change in the pressure chambers, which are in communication with the nozzles.
2. Related Art
A liquid ejecting apparatus is a machine that is provided with a liquid ejecting head that can eject (discharge) liquid. Having such a liquid ejecting head, a liquid ejecting apparatus is capable of ejecting various kinds of liquid. An example of a liquid ejecting apparatus is an image recording apparatus such as an ink-jet printer. An ink-jet printer is provided with an ink-jet recording head, which is an example of various kinds of a liquid ejecting head. An ink-jet printer performs recording by ejecting ink in the form of ink droplets from nozzles of an ink-jet recording head toward a recording target medium such as a sheet of printing paper. As a result of the landing of discharged ink droplets on the surface of a recording target medium, dots are formed thereon. In this way, an ink-jet printer records an image and the like on a recording target medium. An ink-jet recording head is hereinafter simply referred to as a “recording head”. An ink-jet printer is hereinafter simply referred to as a “printer”. These days, the application of such a liquid ejecting apparatus is not limited to an image recording apparatus mentioned above. It is applied to various manufacturing apparatuses. For example, in a display manufacturing apparatus for the production of liquid crystal displays, plasma displays, organic electroluminescence (EL) displays, surface/plane emission displays (FED), or the like, a liquid ejecting apparatus is used as a machine for ejecting various liquid materials such as colorants and electrode materials onto a pixel formation area, an electrode formation area, and the like.
Some recent printers are equipped with a single head unit that has the following structure: a plurality of recording heads is fixed to a head-fixing member such as a sub carriage in a row; each of the plurality of recording heads has a nozzle group that is made up of a plurality of nozzles formed in rows. Some of them are equipped with a capping mechanism that includes a plurality of caps arranged in a row corresponding to the head row (for example, refer to JP-A-2008-273109). Each cap is, for example, is a tray-like member that is made of an elastic material such as elastomer. The top (facing the nozzle formation surface of the corresponding recording head) of the cap is open. When the printer is in a pause state in which a recording head is not used for printing an image and the like on a recording target medium or when operation for forcibly sucking ink, air bubbles, and the like out of the nozzles of a recording head is performed, the capping mechanism brings the top of sidewalls of a cap into contact with the nozzle formation surface of a recording head for sealing (capping). An inner space of the cap that is formed when the cap is in contact with the nozzle formation surface (hereinafter referred to as “sealed space”) is in communication with a waste liquid tank through a waste liquid tube and a suction pump. The suction pump is driven to apply a negative pressure to the sealed space through the waste liquid tube. Due to the negative pressure, ink, air bubbles, and the like are discharged into the sealed space through nozzles. The ink, etc, discharged into the sealed space is drained to the waste liquid tank through the waste liquid tube.
A printer that has a protecting projection formed on a sub carriage has been proposed in the art. The protecting projection is provided for protecting a side and the nozzle formation surface of a recording head. The protecting projection is provided at an end in a direction in which a plurality of recording heads attached to a carriage is arranged in a row. The protecting projection protrudes downward, that is, toward a recording target medium during recording operation, in parallel with a side of a recording head. The front end of the protecting projection is located at the same height as the nozzle formation surface of each of the plurality of recording heads or below the surface. Since such a protecting projection is provided, it is possible to prevent recording paper or the like from coming into contact with a recording head when ink is ejected from the recording head onto the recording paper to print an image and the like thereon.
In such a printer, if each of a plurality of caps corresponding to a plurality of recording heads has a function for sucking ink, the structure of the printer is complex, which results in an increase in cost. To avoid an increase in cost, a printer that has a structure in which not all but some of caps corresponding to a plurality of recording heads have a function for sucking ink has now been being developed in the art. In such a structure, either the group of recording heads or the group of caps is moved relative to the other in a direction in which the recording heads are arranged in a row. By this means, a cap that has the ink-sucking function is brought into contact with a suction target head. With such a structure, it is possible to perform suction operation for all of the recording heads even though it is only some of the caps that have the ink-sucking function. However, such a printer has the following disadvantages. When capping operation is performed in a state in which any cap faces the protecting projection, the collision of the cap and the protecting projection sometimes occurs. In such a case, there is a risk of the sticking of ink from the cap onto the protecting projection. In addition, there is a risk of the dripping of the transferred ink from the protecting projection onto recording paper during printing.